Not a perfect movie, but I'm not sure how they could have done it any better trying to juggle so many characters (DC struggled to balance out 6 characters at once, and this movie had ridiculously more characters compared to Justice League). So overall, pretty impressive. The next movie should be much easier to balance with most of the heroes (and universes population) out of the final battle.
There are a few parts I thought could have been improved, particularly the scene where Ironman, Strange, Spidey, GOTG had Thanos pinned. Screw trying to "remove" the Gauntlet by pulling on it, the goal should have been to cut Thano's arm off and seperating him from his gauntlet's powers (Strange's portal sever move anyone???)... in fact this would have been a great moment to reveal the reality stones ability as a fake out after they thought they had won and maimed Thanos (and would have been a far more effective moment onscreen than the Gamora fakeout on knowhere... which was a of a bit lukewarm scene for me and a bit of a waste of a cool power reveal). Plus, it would solidify the hopelessness of defeating an enemy would already possesses 4 infinity stones by that point (as Strange realises already). Also, at the end Thor should have aimed "Stormbreaker", not at his chest or head... but at his arm as well. It is the most obvious target on Thano's body.
Also, I kind of wish that Strange said there were 2 chances in 14 million plus of them defeating Thanos and then when they fail to get the gauntlet he mumbles under his breath "and now there is only 1" and immediately surrenders the Time Stone. Otherwise it doesn't really make sense why he even bothered to fight Thanos at all after his "future visions" confirmed there was "no other chance".
I also didn't like that Thanos killed all but 1 of the weaponmaking Dwarves. It goes against his own rules and his "morality" goes out the window reducing him to just a jerk. Half of the dwarves should have been spared to maintain consistency, I also felt this way about the slaughter of the surviving Asgardians (more than half has already been lost, it would have been cool for Thanos to be aware and acknowledge that to some degree). Great surprise that he was the Game of Thrones actor though.
Also despite some cool moments, I still think Scarlet Witch was way too underpowered. Not that she could have competed against Thanos once he had the Reality Stone, but still she should have had much more bite than what she currently has (had). Her and Spideys death were the only 2 that surprised me (although that is probably because of owning the original comics). To a lesser degree I was a little surprised that Strange was killed off, mainly because I can't think of anyone else in the current MCU that can possibly fill the shoes of the absent "Adam Warlock" in devising a convincing final strategy.
Where is the "Veronica" 2 satellite? Tony didn't rebuild a new one after the Ultron incident over 2 years ago? That seems unlikely. The only reason the Hulkbuster suit was effective against the Hulk was due to Veronica and would likely be a focus for Tony to rebuild in case the Hulk ever reappeared after his long hiatus.
Bucky's new arm. Considering it is Wakanda tech plus probably made completely of pure vibranium (plus that absorbing kinetic energy tech etc), I was waiting for something awesome... but it never happened. Not sure why it "vanished" along with the rest of his body either. I thought Cap's "Wakanda Shield" was going to be more impressive as well with additional tech abilities, but it was seemingly less effective than his original "frisbee"... a bit disappointing.
I get that there was dialogue from the dwarf mentioning that Thor's new "Stormbreaker" weapon could potentially use the bifrost... but that still doesn't explain WHHHHHHYYYYYYYY???? Doesn't really make any sense. The bifrost is utterly destroyed and Heimdall used the last of its energy contained within himself to get the Hulk to Earth. It would make much more sense if it could "summon dark energy" to transfer between planets instead (with time charge limitations otherwise it is too powerful to use for decapitating dragons like in Ragnorok).
I was so sure that it was Mephisto as the guardian of the Soul Stone, before Red Skull's reveal. And although I was surprised, I couldn't help but feel disappointed. Mephisto would have made so much more sense (as a keeper of dead souls in his job) and would be useful as a character whispering in "gods ear" in the next movie (the literal personification of the "little devil" on Thano's shoulder and potential interpreter for the silent "Lady Death").
I can understand not having Lady Death as the main driving motivation of Thanos... it never fully sat well with me in the comics. But to not have her in it at all? Seems a bit weird, especially after the "to challenge them is to court death" comment at the end of the original Avengers movie being so cool (and now is reduced to something without any meaning at all). Hopefully the "Young Gamora" end scene is actually Lady Death in disguise to taunt Thanos (fingers crossed) she is a shapechager after all. But maybe Gamora's soul is trapped in the Soul Stone as part of the deal to get it. Not sure. But without Lady Death, I'm not sure what Thanos's motivations will be in the next movie... he has apparently already achieved everything he wanted. Seems like he might as well retire to a farm on some distant planet on the other side of the universe happily without any additional motivations.
Plus, no "Watchers" overlooking the end of the universe as we know it? Bit of a shame, particularly after they have already been revealed previously in the MCU and they are definitely going to be watching what is likely to be the most significant moment to "witness" in the universe to date.
Finally, I CANNOT BELIEVE that they missed the opportunity to kill Stan Lee in this movie (as one of the people at the end fading away... in this incarnation the bus driver). Not only because Stan Lee has never died in any of the movies before, and not only because of the symbology of his death along side the deaths of half the Marvel Universe is too perfect, but also his rebirth in the next movie when the Marvel Universe gets (mostly) ressurected. This oversight seems too ridiculously obvious to have lost the opportunity.
I loved the idea of Hulk being defeated so easily for the first time in his life that he is too afraid to come out now. It's a great idea and actually completely original outside of the comics (which I think is really good). It means that Hulk is the coward who only fought because he always thought he couldn't lose... while it is "puny Banner" who is truly brave and fights despite the odds being against him. Banner being the brave adult and Hulk being the cowardly "child" I think may lead to a great moment in the next movie where Hulk and Banner will actually meet for the first time maybe even fight (likely inside Banner's mind). This meeting of minds might even lead to a catalyst of this MCU's version of "Worldbreaker Hulk" being unleashed in the final battle against Thanos.
It is funny that the first thing I walked out of the movie thinking about is how pissed off Rocket will be in the next movie. Not just Groot, but his entire team was wiped out by Thanos. I am having visions of a rabid cybernetic racoon launching a massive succession of "planet destroying" (or even solar system destroying) nuclear/blackhole weaponry at Thanos... even at point blank range if he has to. Especially since he has an equally pissed off nation of a kingless Wakanda and all their technology at his back. Pretty sure they would give Rocket anything he asked for at this point... and "anything" when it comes to Rocket will undoubtably be ridiculously explosive. Plus I don't think "Shuri" faded away who would be extremely angry about her brothers death, and her and Rocket probably can work together to create some fantastic and "never before seen anywhere in the universe" weaponry.
Nebula's survival is also interesting. She has multiple reasons to hate Thanos more than anyone else in the universe... more than Gamora, more than Drax, more than anyone. Thanos becoming a god is not going to sit well with her the most (plus in the original comics she provides a significant moment in the final battle). She is likely the character most willing to do absolutely anything and willing to sacrifice anything (and anyone) to defeat Thanos.
Stark's (and Spidey's) new "nanobot" suits were pretty damn awesome.
So, the irony being that everyone who died in Thano's "half the universe execution finger snap" are all the heroes guaranteed to be ressurected at the end of Infinity War 2 by whoever possesses the Gauntlet after "disarming" Thanos and completely safe. And all the heroes that are still alive now are the only ones at risk of a permenant death in the next movie as they are the ones who get their final onscreen moments before their ultimate sacrifice to save the Marvel universe. It is no fluke that the "survivors" are mainly the actors from the first MCU movies with few movies left in their contacts left. Apart from the deaths of Spidey and Scarlet Witch... this was exactly what I had predicted.
.... noticed a few comments in this thread.
Tony Stark is on a Titan with Nebula and with the Guardians ship parked somewhere nearby. They are not "marooned" (however Nebula's ship was destroyed when she drove it into Thanos).
While I agree, Thano's could have punched Captain America hard enough to make his head seperate from his body, it looked to me like Thano's purposely pulled his punch. He definitely was not punching with any kind of effort, he didn't even wind up, just pushed his fist forward. It was more of a love tap because that was all that was necessary to move onto getting the mind stone. Steve was little more than an annoyance to him at this point and not worth any kind of effort (or getting blood on his nice armor).
Tony Stark is obviously essential in the 1/14, 000, 741 (or whatever) chance of them defeating Thanos, so obviously the loss of the Time Stone was inevitable in all 14 million+ variables. This makes the trade of the stone for Stark's life a no brainer for Strange.
This movie was always going to be a "Thano's wins and the heroes lose" movie. I'm surprised at the amount of people who didn't realise this.
The reason that the heroes that died needed more screen time, and the heroes that survived has less in this movie is...
a) you need to feel the impacts of their deaths at the end of this one and b) the next movie is going to have a lot of the surviving heroes in the final battle who will permenantly die for the next movie. It is basic strategy for emotional manipulation to "feel" the impacts of their deaths (not a criticism, just a fact). More screen time = more audience investment in their loss.